Answer:
D. 50
Step-by-step explanation:
∠CGF and ∠AFG add up 180° because they are same side interior angles. We can write an equation to model the situation:
m∠CGF + m∠AFG = 180°
And, we can substitute:
3x - 20 + x = 180
4x - 20 = 180
4x = 200
x = 50
